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Central PA - Winter 2020/2021


MAG5035
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32 minutes ago, pasnownut said:

Looking at 500’s I’ve seen worse loops in my life. If one is to believe towards the end  we start to see a monster 50/50 retrograde and force everything under. In between it still looks progressive but chances for fun to be had. Just going to need good timing to get it done. 

Yes, blocking can give models a tough time to resolve storms tracks at long range. The good part is that blocking is showing on most guidance.

Someone in the Mid Atlantic forum recently said in reference to blocking, “If you build it, they will come”. I think we will see good storms showing on the models soon for the week between Christmas & New Years.

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8 minutes ago, Blizzard of 93 said:

Yes, blocking can give models a tough time to resolve storms tracks at long range. The good part is that blocking is showing on most guidance.

Someone in the Mid Atlantic forum recently said in reference to blocking, “If you build it, they will come”. I think we will see good storms showing on the models soon for the week between Christmas & New Years.

That’s when the 50/50 starts to show its influence and you can see forcing underneath. Should see more NS energy coming south instead of cutters headed to Wisconsin.  

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I haven't been paying attention to the weather the last few days.  Now I see Williamsport will be warming up and having 1.4" of rain Thursday into Friday. I don't like the icy surfaces we already have.  The cycles of melting and refreezing plus 1.4" of rain on top of that will make for a truly God-awful mess when the day and night temperatures fall back to 32 and below starting on Christmas Day.  The roads and sidewalks weren't icy much last year and I am out of practice balancing.  I don't want to go down!  But as always, there is nothing I can do about the weather.

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When I see this, it is hard not to get excited. This is a pattern that has the potential to deliver winter in a big way for many in the East. The only ones that could potentially lose out would those further north towards New England as the blocking forces the storm track too far south. What we have below is the 5 day mean (day 11-16) from the overnight GEFS. This is the pattern that we are currently transitioning to and gets locked in and looks to have some staying power shortly after our Christmas storm. We are seeing this general look on all 3 major globals (EPS, GEFS, CMC). 

 

What we are seeing is major blocking getting established within the NAO domain (-NAO) which tends to establish troughing in the East and the favorable storm track that comes along with it. To the West we see ridging up through Alaska (-EPO). This is the mechanism to drive cold air into the central portion of the CONUS. Quite often times we will see quick hitting cold shots into the central portion of the country that quickly retreat back into Canada with a -EPO, with only glancing blows in the East. But with the blocking we are seeing this will help to shunt the cold eastward as well as to help lock in the cold. To the west of the -EPO we are seeing an Aleutian low being established. This feature helps to pump energy into the northern and mid-latitude jets from storms that are rotating around it, energy that potentially become our future storms. In the south we are seeing lower heights showing up in the general Texas/New Mexico region. This implies southern energy will be in the mix to possibly seed storms as well. One thing that is not shown is that we are seeing a southern/subtropical jet setting up and having staying power shortly after Christmas, from the deep south/gulf and up off the east coast. This feature would have the ability to provide ample moisture to any storms in the east. What we have here are all the ingredients for a possibly very memorable stretch of winter for some/many in the East. But the devil is in the details, so let's see how this plays out.

GFS500mbDec21.thumb.gif.7e7796da6dcbd7515119a253f05b7ccc.gif

 

I did want to bring up something I alluded to a few days ago. And that was the potential shortly after Christmas. As we near in time to this period and details start emerging I am getting a little more enthusiastic about the prospects. Below we have the 500mb map from the EPS for Sunday the 27th. Both the GEFS and the GEPS also show very similar setups as well. As you can see we have blocking in the NAO region. What we have below that feature is the Christmas day storm that has now rotated up into the 50/50 region and is getting locked in for a period of time. What we are concerned with is the energy/SW located in the central US. As we see this energy move eastward and it closes the gap with the 50/50 low we will see ridging develop between the two systems which will create initial dig from the energy in the central US. This dig will cease once the SW and associated trough start going negative tilt and the storm starts amplifying which will create the desire for the storm to move northward. So what we should see is a storm that digs somewhat into the south and then starts riding northward. Now most times we are concerned about timing between the lead shortwave (50/50 low) and the developing storm as to storm track or even if a storm of any consequence develops at all. If the models are correct this is not so much the case here. What we see here is the 50/50 low gets locked in for a period of time so what will be key here is more so the placement of where it gets locked in then any timing concerns as far as storm track. At this time I am getting somewhat confident we will see a storm in the East (centered roughly around the 28th) and it is more a matter of where the 50/50 sets up as to where the storm track will be. Besides the models being wrong, about the only fly in the ointment to this storm would be with the energy we see off the West coast. If this energy rides too close on the heals of our possible storm then it could/would screw things up.

 

Now about the energy that we see off the West coast. Could we be talking a one, two punch as we see another follow up storm 2/3 days later? If we don't see that energy take an extended stay in the South West or move eastward on the heals of storm #1 I like our prospects for a second storm. 

EPS00zdec21.thumb.gif.e30d8fe54bf62ca1b8dc459d2f16f581.gif

 

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In the short term, there is some light snow on the way by tonight in CTP from a Clipper. 
Maybe I will get a car topper tonight while @MAG5035 is shoveling a few inches of snow.

Here is what CTP sai this morning.

“A fairly vigorous northern stream upper short-wave and clipper type surface system will bring a period of snow to central PA tonight, with the greatest duration and intensity of the snow found from I-99 westward. Although most areas between I-99 and I-81 will only see light accumulations (and just a dusting across the Lower Susq Valley), the higher terrain of the Alleghenies in Northern PA could see an inch or two of snow locally.”

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looking at overnights, you can see the changes starting to happen wrt the southward progression of systems post Christmas, as the blocking is starting to show its teeth, and cutters may now be southern sliders... A much better way to run a winter around here.  Not evident on all models, but GFS suite was notable.  Below is the blocking that is setting up and rolling forward it retrogrades a bit towards being a W based NAO and helps to create a broad trough in conus..  

 gfs-ens_z500a_namer_27.png

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11 minutes ago, pasnownut said:

looking at overnights, you can see the changes starting to happen wrt the southward progression of systems post Christmas, as the blocking is starting to show its teeth, and cutters may now be southern sliders... A much better way to run a winter around here.  Not evident on all models, but GFS suite was notable.  Below is the blocking that is setting up and rolling forward it retrogrades a bit towards being a W based NAO and helps to create a broad trough in conus..  

 gfs-ens_z500a_namer_27.png

It should be exciting times on here over the holidays...tracking and more tracking!

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Seems to me that it's a bad news/good news kind of day. First the bad news:

p120i.gif?1608566419

Above is total QPF we should see over the next 5 days. For those of us east of the mountains, most if not all of that falls as rain. In fact, most of it falls as rain with temps climbing into the 50s. That means - goodbye snowpack, and adios white Christmas. Sort of a shame to lose it on the cusp of Santa's big day, but it is what it is.

Going forward, it sure looks like there are opportunities to rebuild. Personally, the most exciting time of the year for me to have trackable threats is the end of December. Love having trackable threats over the holiday period. I remember last year being void of almost anything to track, so while we'll likely lose what we have now, there's reason to hope for what might be coming soon...

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